A fiber optic gyro (FOG) Sagnac interferometer is used to measure rotation. A directional coupler is often used to direct some light returning from the Sagnac interferometer to a detector. A consequence of using a directional coupler for this purpose is that some of the light from the light source is discarded by the directional coupler before any light enters the Sagnac interferometer.
One useful type of fiber optic gyroscope is disclosed in PCT patent application publication number WO2009/103015, published on Aug. 20, 2009 and entitled “AN INTERFEROMETER EMPLOYING A MULTI-WAVEGUIDE OPTICAL LOOP PATH AND FIBER OPTIC ROTATION RATE SENSOR EMPLOYING SAME,” where the inventor is the same inventor herein. The entire contents of PCT patent application publication number WO2009/103015 are incorporated herein by reference.
Another useful type of fiber optic gyroscope is disclosed in U.S. Pat. No. 7,505,139, issued Mar. 17, 2009 to the same inventor of the present disclosure and entitled “SIGNAL PROCESSING FOR A SAGNAC INTERFEROMETER.” The entire contents of U.S. Pat. No. 7,505,139 are incorporated herein by reference.
The present disclosure presents a new and novel configuration for usefully and effectively employing light that was discarded in previous methods and devices for activating multiple fiber optic gyroscopes.